Selective control of printer motors at outlying telegraph stations



April 26, 1949. J, uss 2,468,074

SELECTIVE TROL OF PRINTER MOTORS AT OUTLYI TEL APH s TIONS Fil Mar 25, l 5

LEE

C D II.

INVEN1 'OR CLARENCE J. RUSSNAK I BY 5 7 ATTORNEY Patented Apr. 26, 1949 SELECTIVE CONTROL OF PRINTER MOTORS AT OUTLYING TELEGRAPH STATIONS Clarence J. Russnak, Chicago, 111., assignor to Teletype Corporation, Chicago, 111., a corporation of Delaware Application March 23, 1945, Serial No. 584,381

6 Claims.

The present invention relates to control circuits, and more particularly to motor control circuits.

In the utilization of telegraph systems wherein there is a central station and a plurality of outlying stations on a signaling channel it is desirable to be able to call in or start a receiving unit at one of the outlying stations without causing the operation of the receiving units at all of the outlying stations. In such a selective system the motors at the various outlying stations need not operate continuously, but only at such times as it is desired to transmit intelligence to a particular station. Likewise, if there is but a single outlying station it is also desirable to call it in at a desired time.

Accordingly, it is the object of the present invention to selectively control printer motors at outlying stations from a central station.

A further object of the invention is to generate selective audio frequencies to control a corresponding tuned circuit at a particular outlying station.

A third object of the invention is to disconnect the selected station motor from operation after the communication is .completed.

The instant apparatus comprises the selective generation of audio frequencies by means of a transitron oscillator, which frequencies are transmitted over the telegraph signaling channel. Each of the outlying stations is provided with a cold cathode tube circuit which has control means tuned to a particular frequency, and which, on the receipt of such frequency causes the operation of the tube and the operation of a relay to establish a printer motor circuit. An electrical contact pair is provided in the printer at each station which is operated upon the receipt of a particular predetermined code signal, to cause an opening of the motor control circuit, with the rendering unoperative of the printer motor.

A more complete understanding may be had of the system and apparatus of the present invention by reference to the attached drawing, wherein such a system is illustrated, taken in conjunction with the following detailed description.

Referring specifically to the drawing, the system contemplates the use of a central station A connected by means of a signaling channel indicated by the numeral l l to a plurality of outlying stations indicated generally by the letters B, C, and D. It is to be understood that the instant invention is not restricted to the use of three outlying s ations, but instead may be utilized with any number thereof, depending on a condition to be described hereinafter. Central station A comprises an audio frequency generator indicated generally by the numeral [2 and a telegraph trandrnitter indicated generally by the numeral l3, such as that shown in Bulletin No. 141, issued in March, 1942, by the Teletype Corporation, Chicago, Illinois.

Referring specifically to the generator l2, such generator comprises a transitron audio oscillator using a pentagrid tube such as the GA? type, well known to those versed in the art. This unit is provided with means for generating a plurality of predetermined frequencies by means of plugs or contacts 14 which upon manual operation insert any one of a plurality of fixed condensers l6 and inductances H in the input circuit of the pentagrid tube. Thus, by means of manual selection of the plugs or contacts It a predetermined frequency will be generated and transmitted through the secondary of the transformer l5 to the signaling channel ll. Therefore, it is possible to generate a plurality of predetermined frequencies depending on the number of plugs or contacts available for inserting varying condensers l6 and inductances I! in the tube input circuit. In the instant example it is to be noted that there are nine such plugs H! which would permit generating of nine distinct frequencies. However, it is obvious that an oscillator generating a single frequency could be provided in the event that there is but a single outlying station.

Referring now to the signaling channel I I, over which both the audio-frequency signals originating from the oscillator l2 and telegraph signals originating from the telegraph transmitter I3 are transmitted, it is comprised of two lines having a D. C. source of potential, represented by the battery H3, in the circuit thereof. Due to the D. C. potential in the signaling chanel l I, it is desirable to place a condenser l9 intermediate the signaling channel and the oscillator 2 to prevent any D. C. current from being fed back to the oscillator from the signaling channel.

It was previously mentioned that there could be any number of outlying stations such as B, C, and D, depending on a condition to be mentioned thereinafter. Accordingly, it is contemplated in the present invention that there may be as many outlying stations, such as B for instance, as there are varying frequencies generated by the audio oscillator [2. In the instant example there is disclosed nine plugs or contacts I4 for inserting condensers l6 and inductances I! to the tube input circuit for the purpose of allowing varying frequencies to be generated and, therefore, there is contemplated nine outlying stations. However, as previously mentioned, inasmuch as there may be more or less than nine plugs or contacts I4, there would be a similar number of outlying stations. Likewise, there may be but one of such stations.

Referring again to the drawing, it is to be noted that the station E, which is disclosed in detail, provides a gas triode tube 2| of the OA4-G type which is of the cold cathode variety. The tube 2| includes an anode or plate 22, a cold cathode 23, and a starter anode 24. Under normal or unoperated condition, the tube 2| is fed from an A. C. source 26 in such a manner that the starter anode 24 is maintained at a potential which is below that required for breakdown by means of the bleeder resistances 2i and 28. Therefore, under this condition the tube will be unoperated. Also provided in the tube circuit is a tuned circuit comprising a condenser 29 and an inductance 3I which is tuned to one of the frequencies which may be generated by the audio frequency generator I2 at the central station A. Each of the outthe signaling channel I by means of a conductor 32 through a band pass filter indicated generally by the numeral 33 and a condenser 34. Further, a low pass filter 35 is also provided for purposes to be later described. Included in the tube circuit is a relay 36 having a pair of armatures 31 land 38.

Also provided at each of the outlying stations is a telegraph receiving unit such, for instance, as that disclosed in U. S. Patent 2,348,214, issued to E. A. Gubisch on May 9, 1944. Such telegraph unit includes an operating motor 4| which is normally unoperative, a line relay 42, and a contact pair 43 under the control of a pull bar 44, the end only of which is shown. In the operation of a receiving unit such as that disclosed in the above-mentioned patent, upon the receipt of certain predetermined code signals thereat, the pull bar such as 44 will be operated to cause the electrical contact 43, associated thereat, to be opened,

thus breaking a previously established electrical circuit.

In the operation of the instant apparatus, as will be described hereinafter, it is to be assumed that the tube circuit disclosed at outlying station E has its tuned circuit comprising the condenser 29 and the inductance 3| tuned to the frequency which will be enerated by the audio frequency generator I 2 at the central station A when the plugs or contacts I4 are in the No. 3 position, as disclosed in the drawing. At such time it is also to be assumed that the telegraph transmitter indicated generally by the numeral I3 at the central station A is not transmittin and that the telegraph receiving unit at outlying station B is in an unoperative condition with its motor 4| not operating.

In order to initiate operation, the plugs will be positioned on the No. 3 contacts, thereby inserting a predetermined value condenser I6 and inductance IT in the input circuit for the pentagrid tube of the audio frequency oscillator I2. At this time a particular frequency will be generated and will be transmitted from the secondary oi the transformer I5 to the signaling channel indicated by the numeral I I It is to be noted that the condenser I9 between the oscillator I2 and the signaling channel II will allow the passage of A. C. current to the signaling channel but will not allow the passage of D. C. potential from the sig naling channel II to the oscillator I2. The audio frequency which is transmitted over the signaling channel I I will pass to all of the outlying stations such as B, C, and D. However, only one station will be responsive to such frequency which, as has been previously mentioned, will be that outlying station (B in the instant example) which has a circuit comprising the condenser 29 and the inductance 3| tuned to that particular frequency.

The selecting frequency current will pass from the signaling channel over the conductor 32, through the filter 33, through the condenser 34, to the condenser 29 and the inductance 3 I, which causes a resonant voltage to appear across the condenser and inductance. A The effect of the voltage across the condenser 29 is to increase the negative potential peaks on the cathode 23 and thus to increase the potentials between the cathode 23 and the startin anode 24. These peaks initiate a discharge between the cathode 23 and the starting anode 24 which produces free ions which enable the discharge to transfer from the starting anode 24 to theanode or plate 22. As a result of such discharge from the cathode 23 to the anode 22, a current will pass from the output circuit of the tube, over the conductor 46, through a winding of the relay 36, to the opposite side of the current source.

Upon the energization of the relay 36, a locking circuit is established which may be traced from one side of the A. C. source 26, through a conductor 41, through a conductor 48, through the closed contact pair 43, through a conductor 49, through a resistance 5|, through the armature 38 which is now attracted due to the energization of the relay 36, through a conductor 52,

through the winding of the relay 36, over a conductor 53, and through a conductor 54 to the opposite side of the A. C. source 26. Therefore, it is obvious that the relay 36 will now remain energized irrespective of the operation of the tube circuit and of the operation of the tube 2|.

Also, upon the energization of the relay 36, a circuit will be established which may be traced from one side of the A. C. source 26, through the conductor 41 to a junction point 56, through a conductor 51, through a manually operable switch 58, through a conductor 59, through the operating winding of motor 4|, through a conductor 6|, through the armature 31, through an electrical contact 62 associated therewith, through a conductor 63 to a junction point 64 with the ocnductor 53, and through the conductors 53 and 54 to the opposite side of the A. C.

source 26. Therefore, at this time the motor 4| cluded from transmitting any further similar audio frequencies. At this time the audio frequency current will no longer be presented to outlying station B and to the circuit associated with the cold cathode tube 2|, and inasmuch as the anode circuit 22 is connected to an A. C. source (through the winding of relay 36) the tube 2| will cease to discharge and the tube will return to its unoperated condition.

It is to be noted that the band pass filter 33 has been provided, in addition to limiting signal transients, so that the low A. 0. potential originating from the source 26 cannot pass over the conductor 32 to the signaling channel H, but so that the high audio frequency current which is transmitted from the central station A may pass therethrough to the circuit associated with the tube 2|. The condenser 34 is also provided so that the D. C. current from the battery it in the signaling channel ll may not pass from the signaling channel to the circuit associated with the tube 2 I; however, this does not prevent the audio frequency current from passing therethrough. The low pass filter 35 allows the power frequency from the A. C. source 25 to pass through the tube circuit, but prevents the selecting frequency passing throug the band pass filter 33 and the condenser 3 from feeding back to the A. C. source 26.

Inasmuch as the motor circuit is now establ lished, the motor 4! will operate to cause the operation of the receiving unit such as that disclosed in the above-mentioned U. S. patent to E, A. Gubisch. The telegraph signals to which this unit will be responsive to, through the line relay 42 in the signaling channel H, will be transmitted from the telegraph transmitter at the central station A, which has been indicated generally by the numeral 13. At such time as there is no more intelligence to be transmitted from the central station A to the outlying station B, a special predetermined signal will be transmitted over the signaling channel H which causes the operation of the telegraph receiver thereat resulting in the operation of the pull bar 44. At such time as the pull bar 44 is operated, the electrical contact pair 43 associated therewith, will be opened and the locking circuit for the relay 36, which previously was traced through this contact pair, will be opened thereby resulting in the relay 36 becoming deenergized. At such time as this occurs, the armature 3'! associated therewith will no longer be held in its attracted position in engagement with the contact 62, but instead will fall away from such contact and cause the circuit which previously had been established through the armature 31 being in engagement with the contact 62 to be broken. This circuit, which is now broken, previously was utilized for the establishment of the electrical circuit for the motor 41. Therefore, at such time as the relay 36 becomes deenergized the motor circuit 4! will be broken and the motor 4| will no longer operate. Thus, the receiving unit at the outlying station B, as exemplified by the motor 4!, the line relay '52, the contact pair 33, and the associated pull bar M, will be rendered unoperative until such time as another audio fre quency current is generated by the oscillator l2 which is of a frequency corresponding to the tuned frequency at the outlying station B, in accordance with the condenser 29 and the induct-- ance 31.

It is to be noted that a switch 58 capable of manual operation is also placed in the motor circuit 4|. Thus, by opening of the switch 58 the circuit for the motor 4| would be broken and the motor would cease to operate. Likewise, in the event that manual switch 58 is in its open position when the audio frequency is transmitted from the central station A, the circuit for the motor ll will never be established and the motor will not operate.

t is to be understood that the apparatus at the other outlying stations, C, D, etc., is identical to that as disclosed and described with respect to outlying station B, and that it operates in a similar manner. The only difference between such outlying station is in the tuned circuit thereat composed of the condenser 29 and the inductance 3i, which are different for each station but which correspond to one of the possible audio frequencies generated by the oscillator l2 at the central station A.

It is to be understood that while a specific embodiment has been described for a particular purpose, that the instant invention is not limited to such particular apparatus and use. For instance, the telegraph transmitter indicated by the numeral it may be altered, as may the number of frequencies generated at the oscillator I2. With respect to the outlying stations such as B, any suitable receiving unit could be provided thereat and the apparatus could be used for purposes other than motor control such as station selection, etc.

What is claimed is:

1. In a communication system, a central station including an oscillator for generating a plurality of different audio frequencies and a telegraph transmitter for generating signaling impulses, a plurality of outlying stations each including a tuned circuit responsive to one only of the generated frequencies and a telegraph receiver responsive to the signaling impulses, a signaling channel connecting said central station and said plurality of outlying stations for carrying said frequencies and said impulses, and means at each outlying station responsive to the operation of said tuned circuit to condition said associated telegraph receiver for operation.

2. In a communication system, a central station including an oscillator for generating a plurality of different audio frequencies and a telegraph transmitter for generating signaling impulses, a plurality of outlying stations each including a tuned circuit responsive to one only of the generated frequencies and a telegraph receiver responsive to the signalin impulses, a signaling channel connecting said central station and said plurality of outlying stations for carrying said frequencies and said impulses, and means including a cold cathode tube at each outlying station responsive to the operation of said tuned circuit to condition said associated telegraph receiver for operation.

3. In a motor control system, a central station including a telegraph transmitter for generating signaling impulses and an oscillator, said oscillator containing a variable capacitance and a variable inductance, means to selectively vary the capacitance and inductance to cause said oscillator to generate a plurality of different audio frequencies, a plurality of outlying stations each including a tuned circuit responsive to one only of the generated frequencies and a telegraph receiver responsive to the signaling impulses, a motor for operating said telegraph receiver, a signaling channel connecting said central station to all of said outlying stations for carrying said frequencies and said impulses, and means at each outlying station responsive to the operation of said tuned circuit to establish a circuit for the operation of said telegraph receiver motor.

4. In a motor control system, a central station including a telegraph transmitter for gen erating signaling impulses and an oscillator having a bank of condensers and a bank of inductances associated with said oscillator, means to select a condenser and an inductance from the respective banks to cause said oscillator to transmit a predetermined frequency, a plurality of outlying stations each including a tuned circuit responsive to one only of the generated frequencies and a telegraph receiver responsive to the signaling impulses, a motor for operating said telegraph receiver, a signaling channel connecting said central station to all of said outlying stations for carrying said frequencies and said impulses, and means including a cold cathode tube at each outlying station responsive to the operation of said tuned circuit to establish a circuit f or the operation of said telegraph receiver motor.

5. In a motor control system, a central station including a telegraph transmitter for generating signaling impulses and an oscillator, said oscillator including a bank of condensers and a bank of induotances, means to selectively place in the operative circuit of said oscillator a condenser and an inductance, said condenser and inductance causing said oscillator to generate a predetermined frequency, a, plurality of outlying stations each including a tuned circuit responsive to one only of the generated frequencies and a telegraph receiver responsive to the signaling impulses having an operating motor, a signaling channel connecting said central station to all of said outlying stations for carrying said frequencies and said impulses, means at each outlying station responsive to the operation of said tuned circuit thereat to establish a circuit for the operation of said telegraph receiver motor, and means in said telegraph receiver responsive to a predetermined signal transmitted from said telegraph transmitter to cause the disestablishment of the motor circuit, thereby rendering said motor unoperative.

6. In a motor control system, a first station including an audio frequency generator and a telegraph signal transmitter, said audio frequency generator containing a variable capacitance and a variable inductance, means to selectively vary the capacitance and inductance of the audio frequency generator to cause said generator to produce a specified frequency, a second station having a motor thereat, a signaling channel connecting said first station and said second station, means at said second station responsive to the generated audio frequency impressed on said signaling channel to cause the operation of said motor, and means at said second station responsive to signals generated by said telegraph transmitter and impressed on said signaling channel to render said motor unoperative.

CLARENCE J. RUSSNAK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,823,978 Jipp Sept. 22, 1931 1,932,679 Ryall Oct. 31, 1933 2,031,934 Corwin Feb. 25, 1936 2,052,581 Richards Sept. 1, 1936 2,068,949 Hollden Jan. 26, 1937 2,070,900 Harris Feb. 16, 1937 2,177,843 Seeley Oct. 31, 1939 2,254,342 Zenner Sept, 2, 1941 2,304,998 Gillespie Dec. 15, 1942 2,315,439 Maxwell Mar. 30, 1945 

